Netopia R7200, User Reference Manual

Page: 89 / 258

IP Setup and Network Address Translation 10-7
Just as an IP address specifies a par ticular computer on a network, por ts are addresses that specify a
par ticular ser vice in a computer. There are many universally agreed-upon por ts assigned to various ser vices.
For example:
■
Web ser vers typically use por t number 80
■
All FTP ser vers use por t number 21
■
Telnet uses por t number 23
■
SNMP uses por t number 161
To help direct incoming IP traffic to the appropriate ser ver, the Netopia R7200 lets you associate these and
other por t numbers with distinct IP addresses on your internal LAN using expor ted ser vices. See
“IP setup” on
page 10-11 for details.
Advanced IP/IPX router configuration options
Advanced users can optionally use connection profiles to configure the IP and IPX protocol stack inter faces on
the SDSL link. You need not explicitly define these parameters, however. The following information is provided
as reference to the possible router configurations advanced users may desire.
The IP router inter face on the SDSL link:
■
may be numbered or unnumbered.
■
may or may not use Network Address Translation (NAT).
■
will attempt to autoconfigure itself without an explicitly configured connection profile, if permitted to do so
by the setting of the Must Match a Defined Profile item in the Default Profile screen. See
“The default
profile” on page 8-6 .
The link up process at the inter face between the SDSL data link encapsulation module and the IP router
functions as follows:
■
When the SDSL data link comes up, the router will search for a configured connection profile that specifies
SDSL encapsulation.
■
If more than one SDSL profile exists, the router will use the first such profile.
■
If no SDSL profile exists, and the Must Match a Defined Profile field in the Default SDSL Profile is set to No,
the router will construct a Default Profile, and the link up process will continue using this constructed
profile as if it were an explicitly configured one.
■
If no SDSL profile exists, and the Must Match a Defined Profile field in the Default SDSL Profile is set to
Yes, IP will not come up on the SDSL link. The router will log an “IP connection refused” event in the WAN
Event Histor y.
■
If an SDSL profile exists (or a default one has been constructed), the router will attempt to configure its
inter face on the SDSL link using the information stored in the profile.